From QB64 Wiki
The VAL Function returns the decimal numerical equivalent value of a STRING numerical value.
- value = VAL(string_value$)
- VAL converts string numbers to numerical values including decimal point values and prefixed "&H" hexadecimal, "&O" octal.
- VAL conversion stops at non-numeric characters except for letter "D" or "E" exponential notation values.
- String values with "D" and "E" letters between numbers may be converted also! EX: VAL("9D4") = 90000
- If the first string character is not a number VAL returns 0. VAL may return erratic values with "%" or "&" starting characters.
- Hexadecimal HEX$ string values with the "&H" prefix can be converted to a decimal value with digits 0 to 9 and letters A to F, like; dec = VAL("&H"+hexvar$).
- Octal OCT$ string values with the "&O" prefix can be converted to a decimal value with digits from 0 to 7 only.
- Presently VAL cannot convert QB64 binary &B prefixed strings from binary to decimal in QB64.
- For character values of ASCII data use ASC to get the value.
- In QB64 use an INTEGER return variable to hold integer values returned by VAL Hex strings: value% = VAL("&HFFFF") = -1
Example 1: Differences in values returned with Qbasic and QB64:
- Explanation: A quirk in Qbasic returned VAL values of 203 for "&" and "&H" that was never fixed until PDS(7.1).
Example 2: Converting a string with some number characters
text$ = "1.23Hello" number! = VAL(text$) PRINT number!
Example 3: Converting literal and variable string values to numerical values.
a$ = "33" PRINT VAL("10") + VAL(a$) + 1
- Explanation: 10 + 33 + 1 = 44, the strings were converted to values.
- You have to convert the string to values in order to use them in a mathematical expression also since mixing strings with numbers isn't allowed. VAL will stop at a text letter so VAL("123G56) would return 123.
- If VAL wasn't used the program would break with an error, as you can't add the value 1 to a string, if the 1 was a string ("1") then the program would return "10331", but now since we used VAL, the numbers were added as they should.
Example 4: Converting a hexadecimal value to decimal value using HEX$ with VAL.
decnumber% = 96 hexnumber$ = "&H" + HEX$(decnumber%) 'convert decimal value to hex and add hex prefix PRINT hexnumber$ decimal% = VAL(hexnumber$) PRINT decimal%
- Explanation: HEX$ converts a decimal number to hexadecimal, but VAL will only recognize it as a valid value with the "&H" prefix. Especially since hexadecimal numbers can use "A" through "F" in them. Create a converter function from this code!